The present invention relates to a video data display control technique. More particularly, the invention relates to a video data display controlling method and a video data display processing system, suitable for systems such as a video data monitoring system using a computer, for displaying a plurality of images on a display screen by changing the display quality of each image or for displaying one image by changing the display quality of an image in a desired partial area.
It is common to display video data supplied from a camera or a VTR on a display screen of a computer system. There are two main systems for displaying video data on a display screen of a computer system. According to one system, supplied video signals are made compatible with computer video signals in an analog level. According to the other system, video signals are sampled and converted into digital video signals and displayed on a display screen of a computer system.
In a communications network interconnecting a plurality of remote computers and transferring data therebetween, it is convenient that video signals can be transferred over the communications network in the same manner as general digital data. The method of converting video signals into digital video signals is therefore becoming a main trend as compared to the method of synthesizing video signals in an analog level.
Real time and data amounts are important considerations when video data is processed in the form of digital data. In a general television, one frame has 525 scan lines in the vertical direction, and a frame rate of 30 frames per second are used. An image in one frame is sampled at 525 .times.525 points in the vertical and horizontal directions so that if one pixel is converted into digital data of 8 bits, the image in one frame has a capacity of 525.times.525 =275625 bytes (about 300 Kbyte). Therefore; at a frame rate of 30 frames per second, a data capacity of 300 Kbyte .times.30 frames =9 MB per second is required. Each image in one frame is required to be displayed during one frame period. If one computer processes digital data of a plurality of images, the total data capacity increases further. As a result, the load of display processing on a computer becomes large, and the transmission load on a communications network becomes large if digital video data is transferred via the network to a video data display unit.
As proposed in JP-A-3-205999, the load of display processing on a computer and a transmission load on a communications path, i.e., a system load, has been reduced conventionally in the following manner. In displaying a plurality of images of subjects to be monitored on a single monitor screen, the frequency of displaying each image is changed in accordance with the running condition of the subject, the importance factor of the subject, or the danger degree of the subject, to thereby reduce the amount of data to be processed and transferred and provide efficient monitoring.
The above-described conventional technique does not consider the degree of display quality of each of a plurality of images displayed on a display screen of a computer. The frequency of displaying video data is changed depending upon only the importance factor of a subject, so that there arises a problem that an image a user really desires to observe cannot be displayed finely.